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Migrants Are on the Rise Around the World, and Myths About Them Are Shaping Attitudes

Immigration is reshaping societies around the globe. Barriers erected by wealthier nations have been unable to keep out those from the global South — typically poor, and often desperate — who come searching for work and a better life. While immigrants have often delivered economic benefits to the countries taking them in, they have also shaken the prevailing order and upended the politics of the industrialized world — where the native-born often exaggerate both their numbers and their needs.

Share of population who are immigrants

0

10%

20%

5%

15%

40%

100%

Canada

22%

Russia 8%

U.S.

15%

U.K. 13%

China 0.1%

Germany 15%

Libya

12%

France 12%

India

0.4%

Switz. 30%

U.A.E.

88%

French

Guiana

40%

Austr.

29%

Lowest-income countries are shown with a stripe pattern.

Share of population who are immigrants

0

10%

20%

5%

15%

40%

100%

Russia

8%

U.K. 13%

Canada

22%

Germany 15%

Kazakh.

20%

France 12%

Switzerland 30%

U.S.

15%

Italy 10%

China

0.1%

Spain 13%

Libya

12%

Saudi

India

0.4%

Arabia

37%

U.A.E.

88%

French Guiana

40%

Equatorial

Guinea

18%

Australia

29%

Lowest-income countries are shown with a stripe pattern.

Share of population who are immigrants

0

10%

20%

5%

15%

40%

100%

Russia

8%

Canada

22%

U.K. 13%

Germany 15%

Kazakh.

20%

France 12%

Switz. 30%

Italy 10%

U.S.

15%

Spain 13%

China

0.1%

Libya

12%

Saudi

Arabia

India

0.4%

37%

U.A.E.

88%

French Guiana

40%

Equatorial

Guinea

18%

Lowest-income countries are shown with a stripe pattern.

Australia

29%

Donald J. Trump’s promise to build a wall to keep Mexicans and Central Americans from crossing the United States’ southern border was central to his successful campaign for the presidency. Antipathy toward immigrants is spreading through Europe, fueling Britons’ desire to leave the European Union, upending Italy’s political establishment and giving the populist Hungarian government of Viktor Orban a fourth term.

Fear of immigrants takes different forms. Immigration from the Middle East and North Africa has led to calls in Europe to prevent its so-called Islamization. In the United States, despite a long history of cultural, religious and ethnic mixing, several studies have concluded that alongside their anger over lost jobs and stagnant wages, many of the non-Hispanic white voters who tipped the presidency to Mr. Trump were motivated by fears that they were losing demographic ground to other groups.

While it is far from a consensus, on both sides of the Atlantic the proposition that immigration amounts to a large-scale threat is gaining ground on the right of the political spectrum.

People perceive there are more immigrants than there really are

A study based on surveys in the United States and a variety of European countries by the economists Alberto Alesina, Armando Miano and Stefanie Stantcheva found that people across the board vastly overstate their immigrant populations.

Actual

Perception of

share of population

who are immigrants

share of population

who are immigrants

United

States

Avg. in

each country

Britain

Germany

France

Sweden

Italy

0

5%

10%

15%

20%

25%

30%

35%

40%

Actual

Perception of

share of population

who are immigrants

share of population

who are immigrants

United States

Average in

each country

Britain

Germany

France

Sweden

Italy

0

5%

10%

15%

20%

25%

30%

35%

40%

Note: For the United States, the number of actual immigrants includes estimates of the illegal immigrant population | Source: “Immigration and Redistribution,” 2018. Alberto Alesina, Armando Miano and Stefanie Stantcheva (Harvard University)

The overestimates are largest among particular groups: the least educated, workers in low-skill occupations with lots of immigrants, and those on the political right. They overstate the share of immigrants who are Muslim and understate the share of Christians. They underestimate immigrants’ education and overestimate both their poverty rate and their dependence on welfare. Almost a quarter of French respondents, as well as nearly one in five Swedes and about one in seven Americans, think the average immigrant gets twice as much government aid as native residents do. In no country is this true.

Actual

Perception of

share of immigrants

who are unemployed

share of immigrants

who are unemployed

Italy

Germany

France

Sweden

Britain

United

States

0

10%

20%

30%

40%

50%

Actual

Perception of

share of immigrants

who are unemployed

share of immigrants

who are unemployed

Italy

Germany

France

Sweden

Britain

United States

0

10%

20%

30%

40%

50%

“People who are are against immigration generate a sense of crisis,” Professor Alesina said. “They create a sense that ‘This is a huge problem; we need a wall.’”

Share of respondents who think the

average immigrant gets twice as much

government aid as natives do

France

Sweden

Italy

United

States

Britain

Germany

0

5%

10%

15%

20%

25%

Share of respondents who think the average immigrant

gets twice as much government aid as natives do

France

Sweden

Italy

United States

Britain

Germany

0

5%

10%

15%

20%

25%

In any event, the sentiment is eroding support for Europe’s social democratic model as well as for the United States’ more limited social safety net. “Just making people think about immigrants generates a strongly negative reaction in terms of redistribution,” Professors Alesina, Miano and Stantcheva write. This raises a fundamental question. If immigration from the South continues apace, will support for the liberal market democracies with robust social safety nets, which have prevailed in northern countries since the middle of the 20th century, hold in the 21st?

The flow of migration varies around the world

MIGRATION IN 1990 IN MILLIONS

NORTH

AMERICA

EUROPE

28

1

6

1

within the

continent

13

4

10

8

2

35

4

2

LATIN

AMERICA

ASIA

1

13

AFRICA

OCEANIA

MIGRATION IN 1990

IN MILLIONS

1

within the

continent

28

EUROPE

NORTH

AMERICA

6

1

13

4

10

8

2

LATIN

AMERICA

ASIA

35

4

2

1

AFRICA

OCEANIA

13

MIGRATION IN 1990

IN MILLIONS

1

within the

continent

28

EUROPE

NORTH

AMERICA

6

1

13

4

10

8

2

LATIN

AMERICA

ASIA

35

4

2

1

AFRICA

OCEANIA

13

MIGRATION IN 1990

IN MILLIONS

1.0

within the

continent

27.9

NORTH

AMERICA

6.2

EUROPE

1.1

13.4

4.4

10.0

8.1

1.8

LATIN

AMERICA

4.0

35.4

ASIA

1.8

1.1

AFRICA

OCEANIA

13.4

MIGRATION IN 1990

IN MILLIONS

1.0

within the

continent

27.9

NORTH

AMERICA

6.2

EUROPE

1.1

13.4

4.4

10.0

8.1

1.8

LATIN

AMERICA

4.0

35.4

ASIA

1.8

1.1

AFRICA

OCEANIA

13.4

Largest diaspora populations in 1990

in millions

Russia

Germany

1.

12.7

11.

3.3

Afghanistan

Kazakhstan

2.

6.7

12.

3.0

India

Turkey

3.

6.7

13.

2.5

Ukraine

Mozambique

4.

5.5

14.

2.2

Bangladesh

Philippines

5.

5.5

15.

2.0

Mexico

Portugal

6.

4.4

16.

1.9

China

Palestine

7.

4.2

17.

1.8

Britain

Belarus

8.

3.8

18.

1.8

Italy

United States

9.

3.4

19.

1.7

Pakistan

Ethiopia

10.

3.3

20.

1.7

Largest diaspora populations in 1990

in millions

Russia

Mexico

Germany

Portugal

1.

12.7

6.

4.4

11.

3.3

16.

1.9

Afghanistan

China

Kazakhstan

Palestine

2.

6.7

7.

4.2

12.

3.0

17.

1.8

India

Britain

Turkey

Belarus

3.

6.7

8.

3.8

13.

2.5

18.

1.8

Ukraine

Italy

Mozambique

United States

4.

5.5

9.

3.4

14.

2.2

19.

1.7

Bangladesh

Pakistan

Philippines

Ethiopia

5.

5.5

10.

3.3

15.

2.0

20.

1.7

Largest diaspora populations in 1990

in millions

Russia

Mexico

Germany

Portugal

Indonesia

1.

12.7

6.

4.4

11.

3.3

16.

1.9

21.

1.6

Afghanistan

China

Kazakhstan

Palestine

Azerbaijan

2.

6.7

7.

4.2

12.

3.0

17.

1.8

22.

1.6

India

Britain

Turkey

Belarus

South Korea

3.

6.7

8.

3.8

13.

2.5

18.

1.8

23.

1.6

Ukraine

Italy

Mozambique

United States

Morocco

4.

5.5

9.

3.4

14.

2.2

19.

1.7

24.

1.6

Bangladesh

Pakistan

Philippines

Ethiopia

Poland

5.

5.5

10.

3.3

15.

2.0

20.

1.7

25.

1.5

Largest diaspora populations in 1990

in millions

Russia

Mexico

Germany

Portugal

Indonesia

Iraq

1.

12.7

6.

4.4

11.

3.3

16.

1.9

21.

1.6

26.

1.5

Afghanistan

China

Kazakhstan

Palestine

Azerbaijan

Spain

2.

6.7

7.

4.2

12.

3.0

17.

1.8

22.

1.6

27.

1.4

India

Britain

Turkey

Belarus

South Korea

Uzbekistan

3.

6.7

8.

3.8

13.

2.5

18.

1.8

23.

1.6

28.

1.4

Ukraine

Italy

Mozambique

United States

Morocco

Egypt

4.

5.5

9.

3.4

14.

2.2

19.

1.7

24.

1.6

29.

1.3

Bangladesh

Pakistan

Philippines

Ethiopia

Poland

El Salvador

5.

5.5

10.

3.3

15.

2.0

20.

1.7

25.

1.5

30.

1.2

Largest diaspora populations in 1990

in millions

Russia

Mexico

Germany

Portugal

Indonesia

Iraq

1.

12.7

6.

4.4

11.

3.3

16.

1.9

21.

1.6

26.

1.5

Afghanistan

China

Kazakhstan

Palestine

Azerbaijan

Spain

2.

6.7

7.

4.2

12.

3.0

17.

1.8

22.

1.6

27.

1.4

India

Britain

Turkey

Belarus

South Korea

Uzbekistan

3.

6.7

8.

3.8

13.

2.5

18.

1.8

23.

1.6

28.

1.4

Ukraine

Italy

Mozambique

United States

Morocco

Egypt

4.

5.5

9.

3.4

14.

2.2

19.

1.7

24.

1.6

29.

1.3

Bangladesh

Pakistan

Philippines

Ethiopia

Poland

El Salvador

5.

5.5

10.

3.3

15.

2.0

20.

1.7

25.

1.5

30.

1.2

Note: Immigration flows from unknown origins not shown. | Source: United Nations Department of Economic and Social Affairs, Population Division

Immigration is unlikely to slow down. All over the world, migration has grown sharply over the last quarter-century. In 1990, fewer than seven million Indians lived abroad, according to calculations from the United Nations. By last year, nearly 17 million lived outside of India. The Mexican diaspora increased to 13 million from 4.4 million over the period. China’s rose to 10 million from 4.2 million.

Most migrants from poor countries never make it to the United States or Western Europe, instead moving to other developing countries nearby. A little over half of emigrants from Africa settle in other African countries, while 60 percent of Asian migrants relocate elsewhere in Asia.

Migration increased the most from Latin America

MIGRATION IN 2017 IN MILLIONS

NORTH

AMERICA

EUROPE

8

41

1

1

17

within the

continent

21

26

1

5

7

9

3

6

63

3

LATIN

AMERICA

ASIA

4

3

1

19

1

AFRICA

OCEANIA

MIGRATION IN 2017

IN MILLIONS

8

41

1

1

NORTH

AMERICA

EUROPE

17

within the

continent

21

26

1

5

7

9

3

LATIN

AMERICA

6

63

ASIA

3

4

3

1

AFRICA

OCEANIA

19

1

MIGRATION IN 2017

IN MILLIONS

1.2

within the

continent

7.6

41.0

1.0

17.2

NORTH

AMERICA

EUROPE

4.6

20.5

9.3

2.6

26.4

1.4

7.1

1.3

LATIN

AMERICA

6.1

63.3

ASIA

4.4

3.1

1.0

3.2

OCEANIA

AFRICA

19.4

1.1

MIGRATION IN 2017

IN MILLIONS

1.2

within the

continent

7.6

41.0

1.0

17.2

NORTH

AMERICA

EUROPE

4.6

20.5

9.3

2.6

26.4

1.4

7.1

1.3

LATIN

AMERICA

63.3

6.1

ASIA

4.4

3.1

1.0

3.2

OCEANIA

AFRICA

19.4

1.1

MIGRATION IN 2017

IN MILLIONS

1.2

within the

continent

7.6

41.0

1.0

17.2

NORTH

AMERICA

EUROPE

4.6

20.5

9.3

2.6

26.4

1.4

7.1

1.3

LATIN

AMERICA

6.1

63.3

ASIA

4.4

3.1

1.0

3.2

OCEANIA

AFRICA

19.4

1.1

Largest diaspora populations in 2017

in millions

India

Afghanistan

1.

16.6

11.

4.8

Mexico

Poland

2.

13.0

12.

4.7

Russia

Indonesia

3.

10.6

13.

4.2

China

Germany

4.

10.0

14.

4.2

Bangladesh

Kazakhstan

5.

7.5

15.

4.1

Syria

Palestine

6.

6.9

16.

3.8

Pakistan

Romania

7.

6.0

17.

3.6

Ukraine

Turkey

8.

5.9

18.

3.4

Philippines

Egypt

9.

5.7

19.

3.4

Britain

Italy

10.

4.9

20.

3.0

Largest diaspora populations in 2017

in millions

India

Syria

Afghanistan

Palestine

1.

16.6

6.

6.9

11.

4.8

16.

3.8

Mexico

Pakistan

Poland

Romania

2.

13.0

7.

6.0

12.

4.7

17.

3.6

Russia

Ukraine

Indonesia

Turkey

3.

10.6

8.

5.9

13.

4.2

18.

3.4

China

Philippines

Germany

Egypt

4.

10.0

9.

5.7

14.

4.2

19.

3.4

Bangladesh

Britain

Kazakhstan

Italy

5.

7.5

10.

4.9

15.

4.1

20.

3.0

Largest diaspora populations in 2017

in millions

India

Syria

Afghanistan

Palestine

United States

1.

16.6

6.

6.9

11.

4.8

16.

3.8

21.

3.0

Mexico

Pakistan

Poland

Romania

Morocco

2.

13.0

7.

6.0

12.

4.7

17.

3.6

22.

2.9

Russia

Ukraine

Indonesia

Turkey

Myanmar

3.

10.6

8.

5.9

13.

4.2

18.

3.4

23.

2.9

China

Philippines

Germany

Egypt

Colombia

4.

10.0

9.

5.7

14.

4.2

19.

3.4

24.

2.7

Bangladesh

Britain

Kazakhstan

Italy

Vietnam

5.

7.5

10.

4.9

15.

4.1

20.

3.0

25.

2.7

Largest diaspora populations in 2017

in millions

India

Syria

Afghanistan

Palestine

United States

South Korea

2.5

1.

16.6

6.

6.9

11.

4.8

16.

3.8

21.

3.0

26.

Mexico

Pakistan

Poland

Romania

Morocco

Portugal

2.

13.0

7.

6.0

12.

4.7

17.

3.6

22.

2.9

27.

2.3

Russia

Ukraine

Indonesia

Turkey

Myanmar

France

3.

10.6

8.

5.9

13.

4.2

18.

3.4

23.

2.9

28.

2.2

China

Philippines

Germany

Egypt

Colombia

Uzbekistan

4.

10.0

9.

5.7

14.

4.2

19.

3.4

24.

2.7

29.

2.0

Bangladesh

Britain

Kazakhstan

Italy

Vietnam

Somalia

5.

7.5

10.

4.9

15.

4.1

20.

3.0

25.

2.7

30.

2.0

Largest diaspora populations in 2017

in millions

India

Syria

Afghanistan

Palestine

United States

South Korea

2.5

1.

16.6

6.

6.9

11.

4.8

16.

3.8

21.

3.0

26.

Mexico

Pakistan

Poland

Romania

Morocco

Portugal

2.

13.0

7.

6.0

12.

4.7

17.

3.6

22.

2.9

27.

2.3

Russia

Ukraine

Indonesia

Turkey

Myanmar

France

3.

10.6

8.

5.9

13.

4.2

18.

3.4

23.

2.9

28.

2.2

China

Philippines

Germany

Egypt

Colombia

Uzbekistan

4.

10.0

9.

5.7

14.

4.2

19.

3.4

24.

2.7

29.

2.0

Bangladesh

Britain

Kazakhstan

Italy

Vietnam

Somalia

5.

7.5

10.

4.9

15.

4.1

20.

3.0

25.

2.7

30.

2.0

Note: Immigration flows from unknown origins not shown. | Source: United Nations Department of Economic and Social Affairs, Population Division

Immigrant populations have risen sharply in most advanced nations

11.6%

More developed

regions

7.2%

Share of population

who are immigrants

World avg.

3.4%

2.9%

1.8%

1.7%

Less developed

regions

’90

’95

’00

’05

’10

’17

11.6%

More developed

regions

7.2%

Share of population

who are immigrants

3.4%

World avg.

2.9%

Less developed regions

1.8%

1.7%

’90

’95

’00

’05

’10

’17

Source: United Nations Department of Economic and Social Affairs, Population Division

The economic pressures pushing migrants from their homes is unlikely to abate soon. But the patterns of migration from the poor South of people seeking a better life in the rich North is likely to change.

Economic and other forces are driving immigration

While instability in Central America continues to drive people north, the vast traffic of low-skilled immigrants into the United States across the southern border has slowed. The demographic bulge of Mexican men in their teens and early 20s who flocked illegally to the United States from the 1990s until the Great Recession has petered out, in part a consequence of declining Mexican fertility since the 1970s. Today, Mexicans are older, on average. Fewer are willing to take the risk. And Mexico’s economy is in better shape than in the 1980s and 1990s, when repeated crises drove many Mexicans from their homes.

There were fewer undocumented immigrants living in the United States in 2016 than in 2007. Apprehensions along the border with Mexico plummeted last year to their lowest level since 1971. Things may change if, say, Mr. Trump decides to leave the North American Free Trade Agreement, setting off another economic crisis in Mexico. Still, the United States seems more likely to suffer from a lack of immigrants than from a continued surge.

Although immigration into the United States might have passed its high-water mark, other parts of the rich world — Europe, notably — are likely to experience more immigration than they have before.

Consider Africa. As Gordon Hanson and Craig McIntosh of the University of California, San Diego, have noted, immigration across the Mediterranean may soon come to look like the vast flows of people who in the 1990s streamed across the Rio Grande.

The number of migrants from sub-Saharan Africa jumped 25 percent over the first decade of this century and surged 31 percent from 2010 to 2017, according to the Pew Research Center. Persistently high fertility rates across Africa have produced a demographic bulge of young people eager to make a better life across the Mediterranean.

Demand for immigrant labor will probably rise in Europe as its population ages. The number of working-age people is already shrinking in many countries. What’s more, migration from many poor African countries is likely to keep rising even as their economies develop: They will remain poor enough for many of their people to crave a better life elsewhere but will become rich enough for more of them to afford the journey.

Notes: Emigrant stocks are the number of people born in each country residing outside that country, divided by national population. Wealth is measured in G.D.P. per person, in 2005 purchasing-power parity U.S. dollars, plotted logarithmically. | Source: Michael A. Clemens (Center for Global Development)

Then there is the wild card, which could well intensify patterns of migration everywhere: climate change.

Global warming is driving migration

Rising average temperatures are already pushing people from their homes in many middle-income countries, according to research by Cristina Cattaneo and Giovanni Peri, increasing migration from rural areas to urban centers and across borders to other nations. As warming continues in the coming decades, it will probably push people from agricultural areas to urban areas and from the global South to the richer global North.

+0.06

El Salvador

Trinidad &

Tobago

Fiji

Cape Verde

Nicaragua

+0.04

Sao Tome

and Principe

Romania

Comoros

Guatemala

Dominican Republic

Bulgaria

+0.02

Haiti

Poland

Honduras

Swaziland

Ecuador

Sierra Leone

TRENDLINE

Ivory Coast

Peru

Bolivia

Philippines

Iraq

South Africa

Thailand

Mauritania

Indonesia

Sri Lanka

Change in

migration

Pakistan

Solomon Islands

India

Egypt

Mongolia

Zimbabwe

Colombia

Iran

Venezuela

Papua New Guinea

China

Syria

Senegal

Angola

Cameroon

Congo

Costa Rica

Saudi Arabia

Lebanon

Vanuatu

Kenya

Morocco

Uruguay

Guinea

Djibouti

Bhutan

Paraguay

Botswana

Samoa

Panama

–0.02

Turkey

Tunisia

Bangladesh

Algeria

–0.04

Logarithmic

scales

Belize

–0.06

–0.2

0

+0.2

+0.4

+0.6

+0.8

+1.0

+1.2

Change in

average temperature

St.Vincent &

Grenadines

+0.08

+0.06

El Salvador

Trinidad &

Tobago

Fiji

Cape Verde

Nicaragua

+0.04

Sao Tome

and Principe

Romania

Comoros

Guatemala

Dominican Republic

Bulgaria

+0.02

Haiti

Poland

Honduras

TRENDLINE

Swaziland

Ecuador

Sierra Leone

Ivory Coast

Peru

Bolivia

Philippines

Iraq

South Africa

Thailand

Mauritania

Change in

migration

Indonesia

Sri Lanka

Pakistan

Solomon Islands

India

Egypt

Mongolia

0

Zimbabwe

Colombia

Iran

Venezuela

Papua New Guinea

China

Syria

Senegal

Angola

Cameroon

Congo

Costa Rica

Saudi Arabia

Lebanon

Vanuatu

Kenya

Morocco

Uruguay

Guinea

Djibouti

Bhutan

Paraguay

Botswana

Samoa

Panama

–0.02

Turkey

Tunisia

Bangladesh

Algeria

–0.04

Logarithmic

scales

Belize

–0.06

–0.2

0

+0.2

+0.4

+0.6

+0.8

+1.0

+1.2

Change in

average temperature

St.Vincent &

Grenadines

+0.08

+0.06

El Salvador

Trinidad &

Tobago

Fiji

Cape Verde

Nicaragua

+0.04

Sao Tome

and Principe

Romania

Comoros

Guatemala

Dominican Republic

Bulgaria

+0.02

Haiti

Poland

Honduras

TRENDLINE

Swaziland

Ecuador

Sierra Leone

Ivory Coast

Peru

Bolivia

Philippines

Iraq

South Africa

Thailand

Mauritania

Change in

migration

Indonesia

Sri Lanka

Pakistan

Solomon Islands

India

Egypt

Mongolia

0

Zimbabwe

Colombia

Iran

Venezuela

Papua New Guinea

China

Syria

Senegal

Angola

Cameroon

Congo

Costa Rica

Saudi Arabia

Lebanon

Vanuatu

Kenya

Morocco

Uruguay

Guinea

Djibouti

Bhutan

Paraguay

Botswana

Samoa

Panama

–0.02

Turkey

Tunisia

Bangladesh

Algeria

–0.04

Logarithmic

scales

Belize

–0.06

–0.2

0

+0.2

+0.4

+0.6

+0.8

+1.0

+1.2

Change in

average temperature

St.Vincent &

Grenadines

+0.08

+0.06

El Salvador

Trinidad &

Tobago

Fiji

Cape Verde

Nicaragua

+0.04

Sao Tome

and Principe

Romania

Comoros

Guatemala

Dominican Republic

Bulgaria

+0.02

Haiti

Poland

Honduras

TRENDLINE

Swaziland

Ecuador

Sierra Leone

Ivory Coast

Peru

Bolivia

Philippines

Iraq

South Africa

Thailand

Mauritania

Change in

migration

Indonesia

Sri Lanka

Pakistan

Solomon Islands

India

Egypt

Mongolia

0

Zimbabwe

Colombia

Iran

Venezuela

Papua New Guinea

China

Syria

Senegal

Angola

Cameroon

Congo

Costa Rica

Saudi Arabia

Lebanon

Vanuatu

Kenya

Morocco

Uruguay

Guinea

Djibouti

Bhutan

Paraguay

Botswana

Samoa

Panama

–0.02

Turkey

Tunisia

Bangladesh

Algeria

–0.04

Logarithmic

scales

Belize

–0.06

–0.2

0

+0.2

+0.4

+0.6

+0.8

+1.0

+1.2

Change in

average

temperature

Notes: The horizontal axis records the natural logarithm of the average temperatures between 2000 and 1981 minus the natural logarithm of the average temperatures between 1960 and 1980. The vertical axis records the difference between the natural logarithms of the average emigration rates between 1990 and 2000 and the emigration rates between 1970 and 1980. | Source: Cristina Cattaneo (Fondazione Eni Enrico Mattei (FEEM)) and Giovanni Peri (University of California, Davis)

The research by Professors Stantcheva, Miano and Alesina suggests that Americans who know an immigrant have more positive perceptions about immigrants’ work ethic, education, dependence on welfare and other behavior. Across the countries in their study, people exposed to positive images of immigrants -- say, about their strong commitment to work -- become much less negative in general about immigration.

Natives’ views can also be manipulated in a negative direction, though, something currently reflected in the politics of many countries. Professor Stantcheva argues that negative portrayals of immigrants in the media could help explain the biased and erroneous views about immigrants’ behavior. And as Professor Alesina notes, “Anti-immigration parties foster these misperceptions in a variety of ways strategically to gain support for their anti-immigration stands.”

But there are already plenty of walls, and they have done little to stop immigration. If rich countries want fewer immigrants, their best shot might be to help poor countries become rich, so that fewer people feel the urge to leave. That would include helping them adapt to climate change, and simply opening up their own markets to developing countries’ exports. “If you want to have fewer immigrants, you would want poorer countries to take advantage of trade,” Professor Alesina said. “The idea that because there is too much immigration you should restrict trade makes no sense.”

What’s more, as Mr. Clemens argues, rich countries should probably start writing new rules and creating new institutions to manage the large immigration flows of the future. They could work to promote new destinations and develop mutually beneficial forms of migration (say, varieties of temporary work visas). They could establish mechanisms to assist vulnerable native-born people, whose jobs might be at stake.